The present invention relates to a tracheal prosthesis intended to replace damaged, diseased or missing tracheal and/or bronchial segments, comprising a plastic shaft provided with a lumen and arranged for having its free ends connected with the tracheal stumps to be joined.
A tracheal prosthesis of this type has been known under the name "Neville Prosthesis".
The use of an artificial trachea is indicated in all cases where extensive damage is found on a trachea, caused for example by accidents, destructive tissue growth and, this occurs particularly frequently, by indwelling respiration hoses if patients have to be treated in intensive-care units for extended periods of time. Given the fact that the trachea is an azygous organ, its proper function is of critical importance for the human organism. Damage caused to the mucosa during long-term artificial respiration frequently leads to subsequent cicatricial constrictions or even complete cicatricial occlusion of the trachea. Moreover, the growth of a cancer may result in occlusion, and accidents may cause breakage of the trachea. In all these cases, respiration through the mouth and the nose is no longer possible, or no longer sufficient.
In order to ensure the required degree of gaseous interchange in the lung, an air passage has to be provided by surgical means; this is effected by opening the throat from the outside (tracheotomy) and introducing a respiratory tube (endotracheal tube). However, in many cases of tracheostenosis speaking is no longer or hardly possible after application of an endotracheal tube. In addition, the faculty of smell is also lost since air no loner passes through the nose. Ventral pressure, which is essential for certain functions of the body, and the stabilization of the thorax (for example when lifting heavy objects) are no longer possible as the respiratory air escapes through the endotracheal tube.
In particular the permanent application of an endotracheal tube, which must receive constant care, impairs the quality of life of a patient quite considerably and leads very frequently to considerable psychological stress.
There have been known different approaches for restoring the physiological respiratory tract. But in all these cases, the the chances of success become lower as the lengths of the tracheal segment to be replaced become longer.
There is the possibility, on the one hand, to expand the constricted trachea with the aid of tubular or bolt-like dummies and, on the other hand, to remove cicatricial constrictions with the aid of a laser beam. But experience shows that such forms of treatment are successful only in certain selected cases of tracheostenosis.
If the trachea is damaged only over a short or a moderate length, for example over 2 cm to 4 cm approximately, the affected segment may be resected. The remaining tracheal stumps are then connected by suturing. This method is no longer applicable in the case of long tracheal defects, and is in any case connected with the risk that the vocal cord nerve may be damaged. A method to replace long tracheal segments consists in skin and cartilage grafting. However, these operations often fail because the newly formed respiratory tract is constricted again by the formation of scar tissue and absorption of the grafted cartilage.
In some rare cases, a complete trachea of a cerebrally dead patient has been transplanted. In these cases, there is a great risk of repulsion of the transplant. Likewise, there have been known cases where preserved trachea segments have been transplanted into the trachea of patients suffering from tracheostenosis. In these cases, there is again the risk of repulsion, but also a risk of absorption of the transplant.
In all cases where the before-described methods cannot be employed, where they fail or are rejected by the patient, an artificial trachea suggests itself as a valuable solution.
The use of a tracheal prosthesis enables an existing tracheal defect to be bridged, irrespective of its length, and in addition the respiratory tract, i.e. the lumen of the prosthesis, can be exactly tuned to the patient, according to his age. The tracheostoma can be closed in such a way that physiological breathing is rendered possible through the mouth and the nose. And in addition normal voice production can be achieved in this way.
The difficulties encountered in connection with the application of tracheal prostheses led to the development of special endotracheal tubes, so-called "Montgomery tubes", i.e. a tubular endoprosthesis for constricted tracheal segments which is inserted into the trachea to keep open the air passage. However, a tube connection branching off at an angle of 90.degree. still leads to the outside, through the tracheostoma. This branch is usually closed, but may be opened for cleaning the T-shaped tube or in emergency cases. While such a "Montgomery-T-tube" actually meets higher demands than a simple endotracheal tube, it still requires tracheotomy which constitutes a heavy stress for the patient. In addition, T tubes tend to get occluded by drying mucus, and voice production is also often impaired as part of the breathing air required for speaking escapes through the tracheostoma.
The tracheal prosthesis that has become known consists of a relatively rigid silicon tube the free ends of which taper conically to the outside. In order to embed the implant more securely, the known silicon tube is provided with a plastic ring on both its upper and its lower ends. The known tracheal prosthesis described before has become known under the name "Neville prosthesis".
The "Neville prosthesis" is much less elastic than the human trachea. In addition, the wall of the prosthesis is very rigid and incapable of yielding to the oesophagus which extends closely beside it. Moreover, mucus adhering to the inside of the lumen can be removed only with great difficulty. This may result in occlusion by mucus. The outer surface of the "Neville prosthesis" being very smooth, the prosthesis may also get dislodged in its bedding. As is well known in the art, this has already led to damage to neighboring organs, fistulae between oesophagus and trachea, and to breakage of large neighboring vessels with haemorrhage of a nature dangerous to life. And the known prosthesis is also not in a position to counteract cicatricial constructions on the tracheal stumps.